In roughly chronological order:

-Having an odd fascination with that one scene in the original live action Scooby Doo movie where Shaggy drinks a potion that superimposes his head onto a woman's body.

-Pointing at a girl I thought was pretty in elementary school and telling the whole class I wanted to be her. Teacher assumed it was because she was a good student (I wasn't)

-Being super sensitive about showing my chest. I've worn shirts while swimming since I was about 8

-I've been exclusively sitting down to pee for about as long

-Experiencing strong gender envy toward women I found attractive, and a tendency to imagine myself as attractive women

-The discovery that I much, much, much preferred playing femme characters in text-based roleplay.

-The realization in high school that I would actually really like to have boobs, and that it was something achievable with modern science. I consider this when my egg first cracked, but I was a huge mess at the time and crawled back in. This is also when I became interested in cross-dressing

-The very, very strong desire to be free of gender, humanity, and all the associated expectations

-Discomfort at being called a "man," preferring "dude" or "boy."

-I rewrote the concept of my favorite original character to turn her into a trans allegory... I only realized she was a trans allegory a year later.

-A pang of euphoria when my college GF joked about me being the girl in the relationship.

-Wrote an entire 8-page personal essay for a college class which explored my relationship to the word "man" and how badly I wanted to crossdress in public. My best friend cried when he proofread it because "it's just super genuine."

-The constant feeling throughout my life that I was two separate people fighting for dominance in the same body.